COMabbr.计算机输出缩微胶片(=computer-output microfilm)abbr.组件对象模型(=Component Object Model)Comsoln.银铅焊料

1. Multiplication of permutations, unlike multiplication of numbers, is not always commutative.
   置换的乘法不同于数的乘法，它并不一定满足交换律。